Статті в журналах з теми "Dynamic processes during acceleration"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Dynamic processes during acceleration.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 статей у журналах для дослідження на тему "Dynamic processes during acceleration".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте статті в журналах для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Pomante, A., L. P. J. Selen, and W. P. Medendorp. "Perception of the dynamic visual vertical during sinusoidal linear motion." Journal of Neurophysiology 118, no. 4 (October 1, 2017): 2499–506. http://dx.doi.org/10.1152/jn.00439.2017.
Повний текст джерелаАнотація:
The vestibular system provides information for spatial orientation. However, this information is ambiguous: because the otoliths sense the gravitoinertial force, they cannot distinguish gravitational and inertial components. As a consequence, prolonged linear acceleration of the head can be interpreted as tilt, referred to as the somatogravic effect. Previous modeling work suggests that the brain disambiguates the otolith signal according to the rules of Bayesian inference, combining noisy canal cues with the a priori assumption that prolonged linear accelerations are unlikely. Within this modeling framework the noise of the vestibular signals affects the dynamic characteristics of the tilt percept during linear whole-body motion. To test this prediction, we devised a novel paradigm to psychometrically characterize the dynamic visual vertical—as a proxy for the tilt percept—during passive sinusoidal linear motion along the interaural axis (0.33 Hz motion frequency, 1.75 m/s2peak acceleration, 80 cm displacement). While subjects ( n=10) kept fixation on a central body-fixed light, a line was briefly flashed (5 ms) at different phases of the motion, the orientation of which had to be judged relative to gravity. Consistent with the model’s prediction, subjects showed a phase-dependent modulation of the dynamic visual vertical, with a subject-specific phase shift with respect to the imposed acceleration signal. The magnitude of this modulation was smaller than predicted, suggesting a contribution of nonvestibular signals to the dynamic visual vertical. Despite their dampening effect, our findings may point to a link between the noise components in the vestibular system and the characteristics of dynamic visual vertical.NEW & NOTEWORTHY A fundamental question in neuroscience is how the brain processes vestibular signals to infer the orientation of the body and objects in space. We show that, under sinusoidal linear motion, systematic error patterns appear in the disambiguation of linear acceleration and spatial orientation. We discuss the dynamics of these illusory percepts in terms of a dynamic Bayesian model that combines uncertainty in the vestibular signals with priors based on the natural statistics of head motion.
2
Zheng, Jingjing, Abuduwaili Abulikemu, Yan Wang, Meini Kong, and Yiwei Liu. "Convection Initiation Associated with the Merger of an Immature Sea-Breeze Front and a Gust Front in Bohai Bay Region, North China: A Case Study." Atmosphere 13, no. 5 (May 6, 2022): 750. http://dx.doi.org/10.3390/atmos13050750.
Повний текст джерелаАнотація:
The mechanism for convection initiation (CI) associated with the merger of an immature sea-breeze front (SBF) and gust front (GF) that occurred in North China on 31 July 2010 was investigated based on both observations and Weather Research and Forecasting (WRF) model simulation. The results show that many CIs occurred continuously in the merging area, and eventually resulted in an intense mesoscale convective system (MCS). The WRF simulation captured the general features of the SBF, GF, their merger processes and associated CIs, as well as the resulting MCS. Quantitative Lagrangian vertical momentum budgets, in which the vertical acceleration was decomposed into dynamic and buoyant components, were conducted along the backward trajectories of air parcels within a convective cell initiated in the merger processes. It was found that both of the dynamic and buoyant accelerations played important roles for the CI. The buoyant acceleration was dominated by the warming due to the latent heat release within the convective cell. Further decomposition of the dynamic acceleration showed the vertical twisting and extension contributed significantly to the dynamic acceleration, while the horizontal curvature was rather small. The vertical twisting was generated due to the vertical shear of horizontal wind, while the extension indicated convergences owing to a mid-level blocking convergence effect and squeezing, and (or) merging of the convergent leading edges of both fronts during their merger processes. The weak convergent leading edge of the immature SBF played an important role for the formation of the convergences.
3
Carey, Jonathan M., Chris I. Massey, Barbara Lyndsell, and David N. Petley. "Displacement mechanisms of slow-moving landslides in response to changes in porewater pressure and dynamic stress." Earth Surface Dynamics 7, no. 3 (August 6, 2019): 707–22. http://dx.doi.org/10.5194/esurf-7-707-2019.
Повний текст джерелаАнотація:
Abstract. Although slow-moving landslides represent a substantial hazard, their detailed mechanisms are still comparatively poorly understood. We have conducted a suite of innovative laboratory experiments using novel equipment to simulate a range of porewater pressure and dynamic stress scenarios on samples collected from a slow-moving landslide complex in New Zealand. We have sought to understand how changes in porewater pressure and ground acceleration during earthquakes influence the movement patterns of slow-moving landslides. Our experiments show that during periods of elevated porewater pressure, displacement rates are influenced by two components: first an absolute stress state component (normal effective stress state) and second a transient stress state component (the rate of change of normal effective stress). During dynamic shear cycles, displacement rates are controlled by the extent to which the forces operating at the shear surface exceed the stress state at the yield acceleration point. The results indicate that during strong earthquake accelerations, strain will increase rapidly with relatively minor increases in the out-of-balance forces. Similar behaviour is seen for the generation of movement through increased porewater pressures. Our results show how the mechanisms of shear zone deformation control the movement patterns of large slow-moving translational landslides, and how they may be mobilised by strong earthquakes and significant rain events.
4
Oh, Ji-Hyun, Xianan Jiang, Duane E. Waliser, Mitchell W. Moncrieff, Richard H. Johnson, and Paul Ciesielski. "A Momentum Budget Analysis of Westerly Wind Events Associated with the Madden–Julian Oscillation during DYNAMO." Journal of the Atmospheric Sciences 72, no. 10 (October 1, 2015): 3780–99. http://dx.doi.org/10.1175/jas-d-15-0044.1.
Повний текст джерелаАнотація:
Abstract The Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign was conducted over the Indian Ocean (IO) from October 2011 to February 2012 to investigate the initiation of the Madden–Julian oscillation (MJO). Three MJOs accompanying westerly wind events (WWEs) occurred in late October, late November, and late December 2011. Momentum budget analysis is conducted to understand the contributions of the dynamical processes involved in the wind evolution associated with the MJO over the IO during DYNAMO using European Centre for Medium-Range Weather Forecasts analysis. This analysis shows that westerly acceleration at lower levels associated with the MJO active phase generally appears to be maintained by the pressure gradient force (PGF), which could be partly canceled by meridional advection of the zonal wind. Westerly acceleration in the midtroposphere tends to be mostly attributable to vertical advection. The results herein imply that there is no simple linear dynamic model that can capture the WWEs associated with the MJO and that nonlinear processes have to be considered. In addition, the MJO in November (MJO2), accompanied by two WWEs (WWE1 and WWE2) spaced a few days apart, is diagnosed. Unlike other WWEs during DYNAMO, horizontal advection is more responsible for the westerly acceleration in the lower troposphere for WWE2 than the PGF. Interactions between the MJO2 envelope and convectively coupled waves (CCWs) are analyzed to illuminate the dynamical contribution of these synoptic-scale equatorial waves to the WWEs. The authors suggest that different developing processes among WWEs can be attributed to different types of CCWs.
5
Hsu, Cheng-Hsing, Jun-Liang Chen, Shan-Chi Yuan, and Kuang-Yuan Kung. "CFD Simulations on the Rotor Dynamics of a Horizontal Axis Wind Turbine Activated from Stationary." Applied Mechanics 2, no. 1 (March 5, 2021): 147–58. http://dx.doi.org/10.3390/applmech2010009.
Повний текст джерелаАнотація:
The adaptive dynamic mesh, user-defined functions, and six degrees of freedom (6DOF) solver provided in ANSYS FLUENT 14 are engaged to simulate the activating processes of the rotor of the Grumman WS33 wind system. The rotor is activated from stationary to steady operation driven by a steady or periodic wind flow and its kinematic properties and power generation during the activating processes. The angular velocity and angular acceleration are calculated directly by the post-processed real-time 6DOF solver without presuming a known rotating speed to the computational grid frame. The maximum angular velocity of the rotor is approximately proportional to the driving wind speed, and its maximal angular acceleration is also closely proportional to the square of the driving wind speed. The evolution curves of the normalized rotor angular velocities and accelerations are almost identical due to the self-similarity properties of the rotor angular velocities and accelerations. The angular velocity of the rotor will reach its steady value. One can use these steady angular velocities to predict the mechanical power generations of the rotor. The momentum analysis theory and the blade element momentum method are applied to predicted power generations and reveal good agreements with experimental data in the low wind speed range.
6
Zhang, Yanbing, Tiehua Ma, Hongyan Zhang, Yaoyan Wu, Zhibo Wu, and Junzhi Yu. "Ground Simulation Tests in Two-Dimensional Dynamic Acceleration Environment." Applied Sciences 10, no. 3 (January 30, 2020): 910. http://dx.doi.org/10.3390/app10030910.
Повний текст джерелаАнотація:
Acceleration environment (AE) simulation tests have been widely applied in various areas such as aviation, space, environmental medicine, medical science, biomedicine, and materials. Most existing AE simulation test methods adopt impact and flight overload simulation separately, which cannot realize the synchronous controllable loading of two-dimensional (2-D) dynamic acceleration. In this paper, we propose and implement an AE simulation test method using an air-cannon-started compound centrifugal turntable. Specifically, our method emphasizes two processes, i.e., orderly transition from impact overload to steady-state overload and synchronous loading of 2-D dynamic AE. To further facilitate the method verification in AE, we develop a specialized simulation test platform. During field tests, axial acceleration of the unit being tested reached 20 g in 0.12 s at the launching stage and radial acceleration raised from zero g to 40 g in 0.5 s at the flight stage, achieving simulation of the 2-D dynamic AE. The obtained results show the effectiveness of the proposed simulation method, shedding light on updated design and control of impact simulation tests on the structures of crystal oscillator circuit, acceleration sensors, and related instruments.
7
Mašek, Bohuslav, Hana Jirková, Jiří Malina, and Štěpán Jeníček. "Advanced Material-Technological Modelling of Complex Dynamic Thermomechanical Processes." Materials Science Forum 654-656 (June 2010): 1594–97. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1594.
Повний текст джерелаАнотація:
Material-technological modelling has made great progress over recent years, thanks to the new possibilities opened up by developments in sensor technology, and especially in new methods of control, supported by innovative electronic elements and electronic circuits. One such device, developed for material-technological modelling, is the thermomechanical simulator which was established in the laboratories of the Research Centre of Forming Technologies FORTECH, in Pilsen, in the Czech Republic. Thanks to new knowledge and technical equipment the majority of technological processes or even technological chains can be modelled. The most considerable and most important innovation in the material-technological modelling process is the significant acceleration and increased precision of the modelling process. The present technology even allows modelling of highly dynamic processes, such as wire rolling including all thermodynamical effects. This paper presents the broad possibilities of the most modern material-technological modelling. The process of detecting technical and manufacturing problems during rolling and the possibilities of failure elimination are introduced in a practical example.
8
Jin, Yong, Daehyeon Kim, Sugeun Jeong, and Hoyeon Kim. "Analysis of Multilayered Ground Amplification Characteristics by Scaled-Down Model Tests." Applied Sciences 12, no. 7 (March 28, 2022): 3432. http://dx.doi.org/10.3390/app12073432.
Повний текст джерелаАнотація:
During an earthquake, seismic waves travel through different media through the source to reach the surface. It is very necessary to study the dynamic characteristics of soil between different layers during earthquake. In order to explore the dynamic characteristics of soil under the action of ground seismic input motion, scaled-down model tests were carried out through 1 g shaking table tests based on a laminar shear box. After creating a dense lower ground with a sample of mixed silica and silty soil, and a loose upper ground with sand, the acceleration was measured by applying seismic loading through the 1 g shaking table test. Through the Peak ground acceleration, Spectral acceleration and Spectral acceleration amplification factors, the magnification variation and differences of each depth of the model and the dynamic characteristics of soil between different layers were displayed. In order to verify the reliability of the experimental data, a one-dimensional ground response analysis was carried out using DEEPSOIL software. The approximate results obtained by comparing each other can provide a basis for the accuracy of the experimental results.
9
Popescu, Radu. "Finite element assessment of the effects of seismic loading rate on soil liquefaction." Canadian Geotechnical Journal 39, no. 2 (April 1, 2002): 331–44. http://dx.doi.org/10.1139/t01-098.
Повний текст джерелаАнотація:
The influence of frequency content of seismic excitation on the extent and pattern of pore-water pressure build-up in saturated soil deposits is addressed. Seismic acceleration time histories are generated as uniformly modulated nonstationary stochastic processes, in accordance with prescribed response spectra and prescribed modulating functions. Based on numerical examples, it is shown that the interplay between the frequency content of seismic excitation and the dynamic characteristics of the soil system and their evolution during and after the earthquake have important implications on the dynamic response.Key words: seismic motion, frequency content, finite elements, soil dynamics.
10
Zhang, Xu, Yan Ma, Chun Mei Yang, and Li Fu. "Dynamic Analysis and Design of the Rhombic Drive of Stirling Engine." Advanced Materials Research 429 (January 2012): 165–71. http://dx.doi.org/10.4028/www.scientific.net/amr.429.165.
Повний текст джерелаАнотація:
The rhombic drive of Stirling engine has been designed in the article, and motion analysis have been carried out according with the requirements of mechanism design in structure. The kinematics mathematical models have been established for rhombic mechanism and the simulation analyses have been carried with the three-dimensional software for the rhombic drive. It makes a point out the optimum position relationship among the link of the rhombic drive during the four processes of the Stirling cycle, and has conducted a mathematical description of piston displacement, velocity and acceleration which drove by the rhombic drive. The simulation curves have showed the relative relationship of position, velocity and acceleration between the two pistons during the body movement. Based on these researches constructive ideas have been offered to improve the rhombic drive in the paper and laid the root for the optimal design of the Stirling engine in theory.
11
Rabus, Bernhard T., and Oliver Lang. "Interannual surface velocity variations of Pine Island Glacier, West Antarctica." Annals of Glaciology 36 (2003): 205–14. http://dx.doi.org/10.3189/172756403781816239.
Повний текст джерелаАнотація:
AbstractThe surface velocity of Pine Island Glacier, West Antarctica, during the period 1992–2000 is measured with synthetic aperture radar feature-tracking techniques. Over the observation period, we find a monotonic acceleration with a spatially uniform amplitude of about 12% of the surface velocity. The acceleration extends > 80 km inland of the grounding line into a zone of prominent arcuate crevasses.The upper limit of these crevasses has migrated up-glacier by 0.2 km a−1 correlated with a velocity increase of similar size in the crevassed zone. On the other hand, there is no clear correlation between the velocity variations and observations of grounding-line migration. These findings suggest ongoing dynamic thinning of Pine Island Glacier, providing independent confirmation of recent interferometric results obtained by Rignot and others (2002).
12
Slivinskas, Kastytis, Vladimir Gichan, Vytautas Striška, and Algimantas Juozas Poška. "Optimization of Transport Movement Parameters of the Transfer Manipulator for the Quenching Bath According to the Technological Process Requirements." Solid State Phenomena 164 (June 2010): 411–18. http://dx.doi.org/10.4028/www.scientific.net/ssp.164.411.
Повний текст джерелаАнотація:
The paper analyzes problems related to optimal selection and possible control of parameters of transport movements of the manipulator serving galvanizing and quenching baths. Evaluation of the acceleration and braking processes as well as minimization of the deflection during oscillations of the suspended loading are considered. Mathematical models of the transfer manipulator together with the loading unit were developed, which enable dynamic evaluation of transporting movements. Calculations of the dynamics of the model and simulations of the transfer process were performed. The obtained research results allow to improve the quality of the processing and reduce the emission of pollutions.
13
Fomin, S. D., V. I. Avramov, D. S. Gapich, and E. S. Vorontsova. "Energy efficiency of the machine-tractor unit in transient modes." Izvestiya MGTU MAMI 11, no. 1 (March 15, 2017): 2–7. http://dx.doi.org/10.17816/2074-0530-66876.
Повний текст джерелаАнотація:
The study of transient modes of operation of the machine-tractor unit (MTU) in order to improve energy efficiency and energy saving is a very important task. The process of starting and accelerating of MTU is the heaviest mode of operation, which is characterized by considerable dynamic loads and which has a significant influence on the most important indicators: productivity, fuel efficiency, as well as slipping of propulsors, abrasion of the soil and tires, loading and lifetime of the elements of the transmission of tractors. One of the effective methods for reducing dynamic loading is the introduction of elastic-damping links in the drive of propulsors of tractors. The study of impact of elastic-damping drive of traction wheels on the parameters of the MTU operation during the acceleration period were carried out in a complex way: theoretically, on the six mass dynamic equivalent model developed by us, which adequately reflects the actual overclocking processes, and experimentally, in the field conditions on full-scale samples. Methods of software mathematical modeling and developed methods of experimental research were used. The complex of the conducted researches has established: due to the decrease in dynamic loads the improvement of all operational parameters of the MTA has been obtained, including: reduction in the slippage of propellers, tire wear and abrasion, a significant increase in energy efficiency: specific fuel consumption in the process of starting and accelerating of MTU with an elastically damping drive on stubble in gears from the third to the sixth decreases by an average of 40% compared to a rigid serial drive. Due to the smoothing of the peaks of the hook load (by 38%) and the torque (by 36%) with the elastic elements, a more smooth and at the same time more intensive acceleration of the unit is obtained (acceleration time is shortened due to the fact that the slippage is reduced and crankshaft speed is reduced in lesser degree).
14
Spivey, R. J., and C. M. Bishop. "Interpretation of body-mounted accelerometry in flying animals and estimation of biomechanical power." Journal of The Royal Society Interface 10, no. 87 (October 6, 2013): 20130404. http://dx.doi.org/10.1098/rsif.2013.0404.
Повний текст джерелаАнотація:
An idealized energy fluctuation model of a bird's body undergoing horizontal flapping flight is developed, focusing on the biomechanical power discernible to a body-mounted accelerometer. Expressions for flight body power constructed from root mean square dynamic body accelerations and wingstroke frequency are derived from first principles and presented in dimensionally appropriate units. As wingstroke frequency increases, the model generally predicts a gradual transition in power from a linear to an asymptotically cubic relationship. However, the onset of this transition and the degree to which this occurs depends upon whether and how forward vibrations are exploited for temporary energy storage and retrieval. While this may vary considerably between species and individual birds, it is found that a quadrature phase arrangement is generally advantageous during level flight. Gravity-aligned vertical acceleration always enters into the calculation of body power, but, whenever forward acceleration becomes relevant, its contribution is subtractive. Several novel kinematic measures descriptive of flapping flight are postulated, offering fresh insights into the processes involved in airborne locomotion. The limitations of the model are briefly discussed, and departures from its predictions during ascending and descending flight evaluated. These findings highlight how body-mounted accelerometers can offer a valuable, insightful and non-invasive technique for investigating the flight of free-ranging birds and bats.
15
Fatland, Dennis R., and Craig S. Lingle. "InSAR observations of the 1993–95 Bering Glacier (Alaska, U.S.A.) surge and a surge hypothesis." Journal of Glaciology 48, no. 162 (2002): 439–51. http://dx.doi.org/10.3189/172756502781831296.
Повний текст джерелаАнотація:
AbstractTime-varying accelerations were observed on Bagley Icefield during the 1993–95 surge of Bering Glacier, Alaska, U.S.A., using repeat-pass synthetic aperture radar interferometry. Observations were from datasets acquired during winter 1991/92 (pre-surge), winter 1993/94 (during the surge) and winter 1995/96 (post-surge). The surge is shown to have extended 110 km up the icefield from Bering Glacier to within 15 km or less of the flow divide. Acceleration and step-like velocity profiles are strongly associated with an along-glacier series of central phase bull’s-eyes with diameters of 0.5–4 km. These bull’s-eyes are interpreted to represent glacier surface rise/fall events of ∼3–30 cm during 1–3 day observation intervals and indicate possible migrating pockets of subglacial water. We present a surge hypothesis that relates late-summer climate to englacial water storage and thence to the subglacial water dynamics — pressurization, hydraulic jacking, depressurization and migration — suggested by our observations.
16
Friedl, Peter, Thorsten C. Seehaus, Anja Wendt, Matthias H. Braun, and Kathrin Höppner. "Recent dynamic changes on Fleming Glacier after the disintegration of Wordie Ice Shelf, Antarctic Peninsula." Cryosphere 12, no. 4 (April 13, 2018): 1347–65. http://dx.doi.org/10.5194/tc-12-1347-2018.
Повний текст джерелаАнотація:
Abstract. The Antarctic Peninsula is one of the world's regions most affected by climate change. Several ice shelves have retreated, thinned or completely disintegrated during recent decades, leading to acceleration and increased calving of their tributary glaciers. Wordie Ice Shelf, located in Marguerite Bay at the south-western side of the Antarctic Peninsula, completely disintegrated in a series of events between the 1960s and the late 1990s. We investigate the long-term dynamics (1994–2016) of Fleming Glacier after the disintegration of Wordie Ice Shelf by analysing various multi-sensor remote sensing data sets. We present a dense time series of synthetic aperture radar (SAR) surface velocities that reveals a rapid acceleration of Fleming Glacier in 2008 and a phase of further gradual acceleration and upstream propagation of high velocities in 2010–2011.The timing in acceleration correlates with strong upwelling events of warm circumpolar deep water (CDW) into Wordie Bay, most likely leading to increased submarine melt. This, together with continuous dynamic thinning and a deep subglacial trough with a retrograde bed slope close to the terminus probably, has induced unpinning of the glacier tongue in 2008 and gradual grounding line retreat between 2010 and 2011. Our data suggest that the glacier's grounding line had retreated by ∼ 6–9 km between 1996 and 2011, which caused ∼ 56 km2 of the glacier tongue to go afloat. The resulting reduction in buttressing explains a median speedup of ∼ 1.3 m d−1 (∼ 27 %) between 2008 and 2011, which we observed along a centre line extending between the grounding line in 1996 and ∼ 16 km upstream. Current median ice thinning rates (2011–2014) along profiles in areas below 1000 m altitude range between ∼ 2.6 to 3.2 m a−1 and are ∼ 70 % higher than between 2004 and 2008. Our study shows that Fleming Glacier is far away from approaching a new equilibrium and that the glacier dynamics are not primarily controlled by the loss of the former ice shelf anymore. Currently, the tongue of Fleming Glacier is grounded in a zone of bedrock elevation between ∼ −400 and −500 m. However, about 3–4 km upstream modelled bedrock topography indicates a retrograde bed which transitions into a deep trough of up to ∼ −1100 m at ∼ 10 km upstream. Hence, this endangers upstream ice masses, which can significantly increase the contribution of Fleming Glacier to sea level rise in the future.
17
Wu, Yudong, Renxian Li, Weiping Ding, Jan Croes, and Mingliang Yang. "Mechanism Study and Reduction of Minivan Interior Booming Noise during Acceleration." Shock and Vibration 2019 (August 29, 2019): 1–17. http://dx.doi.org/10.1155/2019/2190462.
Повний текст джерелаАнотація:
Interior booming noise during acceleration has been one of the most significant NVH problems for minivans. However, the generation mechanism of the interior booming noise remains unclear, so the access to reduce the booming noise is blocked. To solve the booming noise problem, a Source-Path-Receiver-Model-based approach is established to study the generation mechanism of the booming noise. Based on the generation mechanism, several modifications are proposed to reduce the minivan booming noise. In the established approach, the transfer path of the booming noise energy is figured out by the vehicle body and cavity experimental TPA, rear suspension dynamic analysis, and drivetrain torsional vibration analysis. Meanwhile, the vibroacoustic energy in the transfer processes is analyzed quantitatively. The identified generation mechanism is validated by the comparison of the test results of minivan interior noise and the simulation results from the established approach. During the minivan acceleration, the 5th torsional vibration mode (50.5 Hz) of the driveline is excited by the engine torsional vibration around 1500 r/min. Then, the driveline torsional resonance energy is transferred to the body and cavity through the rear suspension and finally leads to the interior booming noise. Based on the validated mechanism, several modifications are proposed to reduce the frequency response function of the driveline, the rear suspension, and the vehicle body around 50 Hz. With these modifications applied to the minivan, it is shown in the experimental results that the interior booming noise is reduced around 1500 r/min engine speed during acceleration. The mechanism study provides effective assistance with minivan interior booming noise reduction and the study approach also could be extended to explore the mechanism of other complex interior noise problems in automobiles.
18
Kindratskyy, В., and R. Litvin. "TRANSITION PROCESSES IN ELECTROMECHANICAL TRANSMISSION WITH A RESILIENT-ELASTIC COUPLING." Municipal economy of cities 1, no. 154 (April 3, 2020): 44–49. http://dx.doi.org/10.33042/2522-1809-2020-1-154-44-49.
Повний текст джерелаАнотація:
Driving systems for hybrid cars and electric vehicles equipped with electric motors have different structures and characteristics. In the vast majority of hybrids, depending on the driving mode, the torque on the wheels of the car can be generated separately by both the internal combustion engine and the electric motor, or by working together. Based on the research results it is established that at the moment of starting the electric motor, the torque in the transmission sections steeply increases to 17 N•m, and for about 1 s decreases to the value of 7 N•m. In the period from 4 to 5.5 s, the torque increases to 14 N•m, which is explained by the overcoming of the inertial load during acceleration of the driven weight, and rapidly decreases to the value of 4 N•m, which corresponds to the consolidated moment of resistance to movement. The electromagnetic moment of electric motor thus also increases steeply in the initial stage of starting the motor up to 66 N•m and after 1 s decreases to the value of 15 N•m. After 5.5 s there is an increase in the moment to the value of 66 N•m and after 5.8 s it stabilizes and ranges from -6 to 22 N•m. In turn, the calculations for an electromechanical transmission equipped with a resilient-elastic coupling showed that the maximum torque in its sections Т2 during the start-up period decreased to 9 N•m, and the acceleration time to a steady turning velocity of the driven weight slightly increased to 6.8 s. The torque that occurs in the transmission sections during acceleration to a steady velocity does not exceed 13 N•m. The torque in the resilient-elastic coupling sections during the start-up period does not exceed 10 N•m, and its value, upon reaching the steady motion of the driven weight, is slightly less than 5 N•m. Peak torque in the resilient-elastic coupling sections Т1 reaches 22 N•m, while in the transmission Т2 it is 13 N•m, which confirms the efficiency of resilient-elastic coupling operation. Thus, the use of resilient-elastic coupling in an electromechanical transmission can reduce the amplitude of the torque in the drive sections during the start-up period by about 1.9 times, as compared to the amplitude of the torque without resilient-elastic coupling, and reduce the peak torque of the transmission sections by 1.7 times. Keywords: asynchronous electric motor, dynamic model, mathematical model, simulation model, torque.
19
Escoubet, C. P., M. G. G. T. Taylor, A. Masson, H. Laakso, J. Volpp, M. Hapgood, and M. L. Goldstein. "Dynamical processes in space: Cluster results." Annales Geophysicae 31, no. 6 (June 13, 2013): 1045–59. http://dx.doi.org/10.5194/angeo-31-1045-2013.
Повний текст джерелаАнотація:
Abstract. After 12 years of operations, the Cluster mission continues to successfully fulfil its scientific objectives. The main goal of the Cluster mission, comprised of four identical spacecraft, is to study in three dimensions small-scale plasma structures in key plasma regions of the Earth's environment: solar wind and bow shock, magnetopause, polar cusps, magnetotail, plasmasphere and auroral zone. During the course of the mission, the relative distance between the four spacecraft has been varied from 20 km to 36 000 km to study the scientific regions of interest at different scales. Since summer 2005, new multi-scale constellations have been implemented, wherein three spacecraft (C1, C2, C3) are separated by 10 000 km, while the fourth one (C4) is at a variable distance ranging between 20 km and 10 000 km from C3. Recent observations were conducted in the auroral acceleration region with the spacecraft separated by 1000s km. We present highlights of the results obtained during the last 12 years on collisionless shocks, magnetopause waves, magnetotail dynamics, plasmaspheric structures, and the auroral acceleration region. In addition, we highlight Cluster results on understanding the impact of Coronal Mass Ejections (CME) on the Earth environment. We will also present Cluster data accessibility through the Cluster Science Data System (CSDS), and the Cluster Active Archive (CAA), which was implemented to provide a permanent and public archive of high resolution Cluster data from all instruments.
20
Zupan, L. H., and D. M. Merfeld. "Neural Processing of Gravito-Inertial Cues in Humans. IV. Influence of Visual Rotational Cues During Roll Optokinetic Stimuli." Journal of Neurophysiology 89, no. 1 (January 1, 2003): 390–400. http://dx.doi.org/10.1152/jn.00513.2001.
Повний текст джерелаАнотація:
Sensory systems often provide ambiguous information. For example, otolith organs measure gravito-inertial force (GIF), the sum of gravitational force and inertial force due to linear acceleration. However, according to Einstein's equivalence principle, a change in gravitational force due to tilt is indistinguishable from a change in inertial force due to translation. Therefore the central nervous system (CNS) must use other sensory cues to distinguish tilt from translation. For example, the CNS might use dynamic visual cues indicating rotation to help determine the orientation of gravity (tilt). This, in turn, might influence the neural processes that estimate linear acceleration, since the CNS might estimate gravity and linear acceleration such that the difference between these estimates matches the measured GIF. Depending on specific sensory information inflow, inaccurate estimates of gravity and linear acceleration can occur. Specifically, we predict that illusory tilt caused by roll optokinetic cues should lead to a horizontal vestibuloocular reflex compensatory for an interaural estimate of linear acceleration, even in the absence of actual linear acceleration. To investigate these predictions, we measured eye movements binocularly using infrared video methods in 17 subjects during and after optokinetic stimulation about the subject's nasooccipital (roll) axis (60°/s, clockwise or counterclockwise). The optokinetic stimulation was applied for 60 s followed by 30 s in darkness. We simultaneously measured subjective roll tilt using a somatosensory bar. Each subject was tested in three different orientations: upright, pitched forward 10°, and pitched backward 10°. Five subjects reported significant subjective roll tilt (>10°) in directions consistent with the direction of the optokinetic stimulation. In addition to torsional optokinetic nystagmus and afternystagmus, we measured a horizontal nystagmus to the right during and following clockwise (CW) stimulation and to the left during and following counterclockwise (CCW) stimulation. These measurements match predictions that subjective tilt in the absence of real tilt should induce a nonzero estimate of interaural linear acceleration and, therefore, a horizontal eye response. Furthermore, as predicted, the horizontal response in the dark was larger for Tilters ( n = 5) than for Non-Tilters ( n= 12).
21
Poliarush, K. A. "INVESTIGATION OF GAS-DYNAMIC PROCESSES IN PIPELINE COMMUNICATIONS DURING THEIR TRENCHLESS RECONSTRUCTION WITH THE TECHNOLOGY "TRACTION PISTON"." Oil and Gas Power Engineering, no. 1(31) (June 26, 2019): 43–53. http://dx.doi.org/10.31471/1993-9868-2019-1(31)-43-53.
Повний текст джерелаАнотація:
The technology of the trenchless reconstruction of pipeline communications "Traction Piston", which consists in running a new polyethylene pipeline into a steel one worn by pigis described. At the same time, in order to maintain the necessary pressure in the cavity, the space between the new polyethylene pipeline and the worn steel one is sealed.
A 3D modeling of the annulus and space behind the piston, where the complex turbulent flow of air flows, is carried out. A CFD modeling of gas-dynamic processes in the annulus and space behind the piston while laying a worn steel pipeline with a polyethylene pipeline in the ANSYS Fluent software system is performed. The mathematical model is based on the solution of the Navier-Stokes equations and the continuity of the flow closed by a two-parameter turbulence model of Launder-Sharma with the use of a wall function with corresponding initial and boundary conditions. A dynamic grid model was used to simulate the motion of the piston and the polyethylene pipeline. The type of adjustment of the dynamic grid parameters during the stroke of a new polyethylene pipeline into a defective steel one – Layering was chosen.
The simulation results were visualized in the postprocessor of the software complex by constructing flow lines, velocity vectors, pressure fields on the contours and in the longitudinal section of the annulus and space behind the piston. The exact values of velocity, pressure at different points between the annulus and space behind the piston were determined. The structure of the air flow in the cavity and interstitial space is studied. The places of slowdown and acceleration of air flow, falling and increase of pressure are found. The loss of pressure in the annular space is determined.
22
Span, N., M. H. Kuhn, and H. Schneider. "100 years of ice dynamics of Hintereisferner, Central Alps, Austria, 1894–1994." Annals of Glaciology 24 (1997): 297–302. http://dx.doi.org/10.1017/s0260305500012349.
Повний текст джерелаАнотація:
Velocity measurements carried out on Hintereisferner, Central Alps, Austria, provide the unique opportunity to study 100 years of ice dynamics of this glacier. During this time, three periods of accelerated flow occurred, around 1920, in 1940 and in the 1970s; but only around 1920 did the acceleration actually lead to an advance of about 60 m. The velocity increased from 30 m year−1 in 1914 to more than 120 m year−1 in 1919, and doubled during the accelerations of 1940 and 1980. In the course of the third event, the velocity increase spread over a period of more than a decade (1965–79) with a comparatively low maximum. These velocity changes cannot be explained by increased deformation velocity due to increased ice thickness alone. Time series of the velocities at various locations along the glacier are given for the entire period, and an attempt was made to construct a time series of the velocity at a point 2 km from the strongly retreating front. The flow divergence was about 0.1 per year in the lowest 2 km, and emergence velocities reached 5 myear−1.
23
Span, N., M. H. Kuhn, and H. Schneider. "100 years of ice dynamics of Hintereisferner, Central Alps, Austria, 1894–1994." Annals of Glaciology 24 (1997): 297–302. http://dx.doi.org/10.3189/s0260305500012349.
Повний текст джерелаАнотація:
Velocity measurements carried out on Hintereisferner, Central Alps, Austria, provide the unique opportunity to study 100 years of ice dynamics of this glacier. During this time, three periods of accelerated flow occurred, around 1920, in 1940 and in the 1970s; but only around 1920 did the acceleration actually lead to an advance of about 60 m. The velocity increased from 30 m year−1 in 1914 to more than 120 m year−1 in 1919, and doubled during the accelerations of 1940 and 1980. In the course of the third event, the velocity increase spread over a period of more than a decade (1965–79) with a comparatively low maximum. These velocity changes cannot be explained by increased deformation velocity due to increased ice thickness alone.Time series of the velocities at various locations along the glacier are given for the entire period, and an attempt was made to construct a time series of the velocity at a point 2 km from the strongly retreating front. The flow divergence was about 0.1 per year in the lowest 2 km, and emergence velocities reached 5 myear−1.
24
Stets, A. A. "Approximating Damped Vibrations of Large Space Structures." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 3 (96) (June 2021): 64–76. http://dx.doi.org/10.18698/1812-3368-2021-3-64-76.
Повний текст джерелаАнотація:
It is possible to use data recorded by onboard acceleration sensors to verify mathematical models of large modular space structures in terms of simulating dynamic processes. The paper investigates an approach to approximating damped oscillations caused by dynamic impacts during operation. Initially, we approximate the response of the structure by summing damped harmonics derived from analysing the frequency spectrum of the dynamic process; then we use the Levenberg --- Marquardt algorithm in the parameter space of the harmonic set to find the best match between the real dynamic process and its approximation. We propose a modification of the approach considered which involves employing single harmonics to perform successive approximations of the function of time to be fitted. We show that it is possible to apply the approach proposed to identifying the frequency and dissipative parameters of the structure under consideration. The paper presents the results of testing the approach proposed via artificially generated noisy acceleration functions of time with known parameters, which were reconstructed with a sufficient degree of accuracy. A real-world example provided comprises the results of analysing the ISS accelerometer readings recorded against the background of damped vibrations in its structure that were caused by burns of its attitude control engines
25
Ramsey, Daniel K., and Ryan L. Crotin. "Stride Length Impacts on Sagittal Knee Biomechanics in Flat Ground Baseball Pitching." Applied Sciences 12, no. 3 (January 19, 2022): 995. http://dx.doi.org/10.3390/app12030995.
Повний текст джерелаАнотація:
Coordinated lower extremity biomechanics are altered in response to changes in stride length, influencing the kinetic chain that potentially induces compensatory throwing mechanics throughout the baseball pitching cycle. The respective sagittal knee dynamic profiles, for both the stride (lead) and drive (trail) leg, were analyzed during flat ground baseball pitching to determine whether the stride length variation elicits compensatory drive and stride leg knee joint kinematics, kinetics, and joint powers. Using a randomized cross-over design, a cohort of 19 healthy skilled competitive pitchers from collegiate and high school travel programs from across Western New York were assigned to throw 2 simulated 80 pitch games at ±25% of their desired stride length. An integrated motion capture system with two force plates and a radar gun tracked each throw. Pairwise comparisons at hallmark events and phases identified significantly different sagittal knee dynamics for both the drive and stride leg between the stride length conditions. During the acceleration phase, the drive knee moments between the stride length conditions demonstrated differences in power generation and absorption. Longer strides allowed for greater knee propulsion dynamics, exemplified by eccentric drive knee extensor moments with a concomitant power absorption that slowed the rate of drive knee flexion (p ≤ 0.001). Conversely, shorter strides generated power through concentric knee flexor moments that increased the rate of drive knee flexion (p ≤ 0.001). Stride knee extensor moments and power generation during the acceleration phase were also significantly higher with shorter strides (p ≤ 0.05). Adapted knee joint dynamics may offer insights into stride length optimization, training, and injury prevention strategies.
26
Muresan, I. S., S. A. Khan, A. Aschwanden, C. Khroulev, T. Van Dam, J. Bamber, M. R. van den Broeke, B. Wouters, P. Kuipers Munneke, and K. H. Kjær. "Glacier dynamics over the last quarter of a century at Jakobshavn Isbræ." Cryosphere Discussions 9, no. 5 (September 14, 2015): 4865–92. http://dx.doi.org/10.5194/tcd-9-4865-2015.
Повний текст джерелаАнотація:
Abstract. Observations over the past two decades show substantial ice loss associated with the speedup of marine terminating glaciers in Greenland. Here we use a regional 3-D outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI) located in west Greenland. Using atmospheric and oceanic forcing we tune our model to reproduce the observed frontal changes of JI during 1990–2014. We identify two major accelerations. The first occurs in 1998, and is triggered by moderate thinning prior to 1998. The second acceleration, which starts in 2003 and peaks in summer 2004, is triggered by the final breakup of the floating tongue, which generates a reduction in buttressing at the JI terminus. This results in further thinning, and as the slope steepens inland, sustained high velocities have been observed at JI over the last decade. As opposed to other regions on the Greenland Ice Sheet (GrIS), where dynamically induced mass loss has slowed down over recent years, both modelled and observed results for JI suggest a continuation of the acceleration in mass loss. Further, we find that our model is not able to capture the 2012 peak in the observed velocities. Our analysis suggests that the 2012 acceleration of JI is likely the result of an exceptionally long melt season dominated by extreme melt events. Considering that such extreme surface melt events are expected to intensify in the future, our findings suggest that the 21st century projections of the GrIS mass loss and the future sea level rise may be larger than predicted by existing modelling results.
27
Ding, Wei, Chuanteng Lu, Qiancheng Xie, Xiaofeng Luo, and Gongjin Zhang. "Understanding the Settling Processes of Dredged Sediment Disposed in Open Waters through Experimental Tests and Numerical Simulations." Journal of Marine Science and Engineering 10, no. 2 (February 7, 2022): 220. http://dx.doi.org/10.3390/jmse10020220.
Повний текст джерелаАнотація:
During dredging for subsea tunnels and pipelines, the dredged soil is typically dumped in a designated area. Understanding the settling behaviors of the dumped particles is essential for an accurate prediction of the resulting morphology. This study dealt with the settling processes in the open-water column by means of experimental tests and numerical simulations. Both quiescent and ambient current conditions were taken into account. Particular attention was paid to the induced flow patterns, descent sediment movement features and the resulting topography. Regarding the diffusion width and settling velocity, three key effect factors, i.e., dumped volume, particle size and ambient flow strength, were considered. The results show that the dumped sediment in the water forms a particle cloud, and two vortices with opposite rotations occur on both sides of the cloud. During settlement, three stages corresponding to convective descent, dynamic collapse and passive diffusion are observed. Most of the descending sediment is incorporated in a spherical vortex, resembling an upside-down mushroom cloud, and some sediment is also contained in an irregular trailing stem. The dumped particles exhibit initial acceleration, and then they slow down to converge to a fixed value. Subjected to the ambient currents, the initial acceleration phase is prolonged, and the vortex is somewhat distorted; the particle cloud is also advected downstream with a velocity roughly equal to the ambient current.
28
Gendrich, C. P., M. M. Koochesfahani, and M. R. Visbal. "Effects of Initial Acceleration on the Flow Field Development Around Rapidly Pitching Airfoils." Journal of Fluids Engineering 117, no. 1 (March 1, 1995): 45–49. http://dx.doi.org/10.1115/1.2816817.
Повний текст джерелаАнотація:
Computational results are presented to show how the acceleration period at the start of nominally constant pitch rate trajectories affects the dynamic stall process. Large amplitude motions of an NACA 0012 airfoil pitching about the quarter-chord axis were studied using constant (ON/OFF) acceleration profiles with nondimensional acceleration periods ranging between 0.039 to 0.6, and large pitch rates (0.1 ≤ Ω* ≡ α˙ c/2U∞≤0.4). The initial acceleration is observed to affect the integrated loads, surface pressure distribution, and the evolution of reversed flow regions just above the surface of the airfoil only during the acceleration period and for a relatively short time δτ ≤ 0.25 afterwards; τ≡ tU∞/c. After that time, all of these quantities only depend on the instantaneous angle of attack for a given pitch rate. These results are consistent with and explain previous experimental flow visualization observations. The onset of leading edge separation at high and low pitch rates is shown to be characterized by different processes. At low pitch rates leading edge separation occurs after the reversed flow front originating at the trailing edge has reached the leading edge. At higher pitch rates leading edge separation and the upstream progression of the (trailing edge) reversed flow front develop independently.
29
Oleksik, Mihaela, Dan Dobrotă, Mădălin Tomescu, and Valentin Petrescu. "Improving the Performance of Steel Machining Processes through Cutting by Vibration Control." Materials 14, no. 19 (September 30, 2021): 5712. http://dx.doi.org/10.3390/ma14195712.
Повний текст джерелаАнотація:
Machining processes through cutting are accompanied by dynamic phenomena that influence the quality of the processed surfaces. Thus, this research aimed to design, make, and use a tool with optimal functional geometry, which allowed a reduction of the dynamic phenomena that occur in the cutting process. In order to carry out the research, the process of cutting by front turning with transversal advance was taken into account. Additionally, semi-finished products with a diameter of Ø = 150 mm made of C45 steel were chosen for processing (1.0503). The manufacturing processes were performed with the help of two tools: a cutting tool, the classic construction version, and another that was the improved construction version. In the first stage of the research, an analysis was made of the vibrations that appear in the cutting process when using the two types of tools. Vibration analysis considered the following: use of the Fast Fourier Transform (FFT) method, application of the Short-Time Fourier-Transformation (STFT) method, and observation of the acceleration of vibrations recorded during processing. After the vibration analysis, the roughness of the surfaces was measured and the parameter Ra was taken into account, but a series of diagrams were also drawn regarding the curved profiles, filtered profiles, and Abbott–Firestone curve. The research showed that use of the tool that is the improved constructive variant allows accentuated reduction of vibrations correlated with an improvement of the quality of the processed surfaces.
30
Brun, J. P., C. Faccenna, F. Gueydan, D. Sokoutis, M. Philippon, K. Kydonakis, and C. Gorini. "EFFECTS OF SLAB ROLLBACK ACCELERATION ON AEGEAN EXTENSION." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 5. http://dx.doi.org/10.12681/bgsg.11697.
Повний текст джерелаАнотація:
Aegean extension is a process driven by slab rollback that, since 45 Ma, shows a twostage evolution. From Middle Eocene to Middle Miocene it is accommodated by localized deformation leading to i) the exhumation of high-pressure metamorphic rocks from mantle to crustal depths, ii) the exhumation of high-temperature rocks in core complexes and iii) the deposition of Paleogene sedimentary basins. Since Middle Miocene, extension is distributed over the whole Aegean domain giving a widespread development of onshore and offshore Neogene sedimentary basins. We reconstructed this two-stage evolution in 3D at Aegean scale by using available ages of metamorphic and sedimentary processes, geometry and kinematics of ductile deformation, paleomagnetic data and available tomographic models. The restorationmodel shows that the rate of trench retreat was around 0.6 cm/y during the first 30 My and then accelerated up to 3.2 cm/y during the last 15 My. The sharp transition observed in the mode of extension, localized versus distributed, which occurred in Middle Miocene correlates with the acceleration of trench retreat and is more likely a consequence of the Hellenic slab tearing documented by mantle tomography. The development of large dextral NE-SW strike-slip faults during the second stage of Aegean extension, since Middle Miocene, is illustrated by the 450 Km-long fault, recently put in evidence, offshore from Myrthes to Ikaria and onshore from Izmir to Balikeshir, in western Anatolia. Therefore, the interaction between the Hellenic trench retreat and the westward displacement of Anatolia started in Middle Miocene,almost 10 Ma before the propagation of the North Anatolian Fault in the North Aegean. This raises a fundamental issue concerning the dynamic relationship between slab tearing and Anatolia displacement.
31
Fang, Yuan, and Fan Tian Xia. "Dynamic Research of Knitting Element for Computerized Flat Knitting Machine Based on ANSYS/LS-DYNA." Advanced Materials Research 472-475 (February 2012): 488–93. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.488.
Повний текст джерелаАнотація:
Based on research on the knitting processes, an impact mechanic model for knitting elements was established to investigate the variation of the impact force in vertical direction between the cam and the select jack. The variation of the displacement, velocity, acceleration of the select jack and the stability for the needles’ moving has been confirmed by the simulation of knitting process based on the software ANSYS/LS-DYNA. Furthermore, the variation of the select jack has been confirmed by experimental measurement during the knitting process. The data of the experiment results were in accordance with the ANSYS’ simulation which verified the correctness of the ANSYS’ analysis. It provided a theoretic basis for the design of computerized flat knitting machines.
32
SAKAKIBARA, DAIKI, and SHIN SUGIYAMA. "Ice front and flow speed variations of marine-terminating outlet glaciers along the coast of Prudhoe Land, northwestern Greenland." Journal of Glaciology 64, no. 244 (March 16, 2018): 300–310. http://dx.doi.org/10.1017/jog.2018.20.
Повний текст джерелаАнотація:
ABSTRACTSatellite images were analyzed to measure the frontal positions and ice speeds of 19 marine-terminating outlet glaciers along the coast of Prudhoe Land, northwestern Greenland from 1987 to 2014. All the studied glaciers retreated over the study period at a rate of between 12 and 200 m a−1, with a median (mean) retreat rate of 30 (40) m a−1. The glacier retreat began in the year ~2000, which coincided with an increase in summer mean air temperature from 1.4 to 5.5 °C between 1996 and 2000 in this region. Ice speed near the front of the studied glaciers ranged between 20 and 1740 m a−1 in 2014, and many of them accelerated in the early 2000s. In general, the faster retreat was observed at the glaciers that experienced greater acceleration, as represented by Tracy Glacier, which experienced a retreat of 200 m a−1 and a velocity increase of 930 m a−1 during the study period. A possible interpretation of this observation is that flow acceleration induced dynamic thinning near the termini, resulting in enhanced calving and rapid retreat of the studied glaciers. We hypothesize that atmospheric warming conditions in the late 1990s triggered glacier retreat in northwestern Greenland since 2000.
33
Volkovsky, A., and V. Makarov. "Chip formation processes based on orthogonal processing of polymer composite materials." Journal of Physics: Conference Series 2131, no. 4 (December 1, 2021): 042018. http://dx.doi.org/10.1088/1742-6596/2131/4/042018.
Повний текст джерелаАнотація:
Abstract This paper presents the results of the study of processes occurring in the cutting zone during the processing of polymer composite materials. The research included determining the effects of orthogonal cutting conditions, such as the cutting depth t and cutting rate v, on the tangential component Pz of the cutting force, the length lc of chips, as well as the vibration acceleration W, to clarify the results previously submitted to the scientific community and obtain new data. The study included 12 experiments for different cutting conditions with the cutting depth t varying in the range of 0.1—0.4 mm and the cutting rate — in the range of 6.7—30.2 m/min. The experimental results allowed to determine a range of cutting rates that lead to a low level of elastic deformations of reinforcing fibers. Based on the dynamics of increasing cutting forces in various cutting conditions, tool cutting edge wear, type and length of chips, as well as the vibration acceleration dynamics, we have found that reinforcing composite material fibers accumulate on the tool cutting edge, while elastic fracture of these fibers causes defect formation on the processed surface. The analysis allows giving recommendations on the need for research in the field of abrasive machining with rigid grinding wheels due to the highest hardness of the cutting tool surface, increased machining speed and the possibility of self-sharpening during tool wear.
34
Tsutaki, Shun, Shin Sugiyama, Daisuke Nishimura, and Martin Funk. "Acceleration and flotation of a glacier terminus during formation of a proglacial lake in Rhonegletscher, Switzerland." Journal of Glaciology 59, no. 215 (2013): 559–70. http://dx.doi.org/10.3189/2013jog12j107.
Повний текст джерелаАнотація:
AbstractIn 2005 the ongoing retreat of Rhonegletscher, Switzerland, led to the formation of a proglacial lake. To investigate the influence of proglacial lake formation on the dynamics and evolution of glaciers, we measured horizontal flow velocity, vertical ice motion and water levels in boreholes with high spatial resolutions during the summer seasons of 2007–09. Annual flow speeds near the terminus increased by a factor of 2.7 from 2005/06 to 2007/08, and exceeded 20 m a−1 in 2009. The velocity increased towards the glacier front, indicating that the ice was thinning under a longitudinally stretching flow regime. Our observations show that the increase in flow speed near the terminus was due to increases in basal motion as a result of ice thinning. During summer 2009, the ice surface at the terminus moved vertically upwards by up to 4.69 m as the ice began to float on the lake. The observed ice motion can be explained by the upward bending of marginal ice and the formation of faults that cut through the entire ice thickness. We predict that if the current ice thinning continues, the basal water pressure will exceed the pressure exerted by the ice overburden, and the glacier will progressively disintegrate over an expanding area.
35
Yang, Lan-tao, Yi-min Shao, Wei-wei Jiang, Lu-ke Zhang, Li-ming Wang, and Jin Xu. "Effects of Tooth Surface Crack Propagation on Meshing Stiffness and Vibration Characteristic of Spur Gear System." Applied Sciences 11, no. 4 (February 23, 2021): 1968. http://dx.doi.org/10.3390/app11041968.
Повний текст джерелаАнотація:
Tooth surface cracks are considered as the early stage of the development of tooth surface spalling failure. Understanding the excitation mechanism of surface cracks has a great significance in the early diagnosis of spalling faults. However, there are few studies on the dynamic modelling of surface cracks, and the influence mechanism of surface cracking on the dynamic characteristics of a gear system is also not yet clear during its propagation process. Thus, an analytical calculation model of the meshing stiffness of gear with tooth surface crack is developed. Then, a dynamic model of a spur gear system with six degrees of freedom (DOF) is established based on the proposed surface crack calculation model. The effects of surface crack propagation on the meshing stiffness and dynamic characteristics of gear system are investigated. The results show that the side frequencies of dynamic transmission error (DTE) are more sensitive than those of the acceleration responses during the surface crack propagation, which is more favorable to the surface crack fault diagnosis. Compared to the traditional spalling fault model, the proposed model can accurately characterize the dynamic characteristics of a gear system with the early spalling defect.
36
Harper, Joel, Toby Meierbachtol, Neil Humphrey, Jun Saito, and Aidan Stansberry. "Generation and fate of basal meltwater during winter, western Greenland Ice Sheet." Cryosphere 15, no. 12 (December 7, 2021): 5409–21. http://dx.doi.org/10.5194/tc-15-5409-2021.
Повний текст джерелаАнотація:
Abstract. Basal sliding in the ablation zone of the Greenland Ice Sheet is closely associated with water from surface melt introduced to the bed in summer, yet melting of basal ice also generates subglacial water year-round. Assessments of basal melt rely on modeling with results strongly dependent upon assumptions with poor observational constraints. Here we use surface and borehole measurements to investigate the generation and fate of basal meltwater in the ablation zone of Isunnguata Sermia basin, western Greenland. The observational data are used to constrain estimates of the heat and water balances, providing insights into subglacial hydrology during the winter months when surface melt is minimal or nonexistent. Despite relatively slow ice flow speeds during winter, the basal meltwater generation from sliding friction remains manyfold greater than that due to geothermal heat flux. A steady acceleration of ice flow over the winter period at our borehole sites can cause the rate of basal water generation to increase by up to 20 %. Borehole measurements show high but steady basal water pressure rather than monotonically increasing pressure. Ice and groundwater sinks for water do not likely have sufficient capacity to accommodate the meltwater generated in winter. Analysis of basal cavity dynamics suggests that cavity opening associated with flow acceleration likely accommodates only a portion of the basal meltwater, implying that a residual is routed to the terminus through a poorly connected drainage system. A forcing from cavity expansion at high pressure may explain observations of winter acceleration in western Greenland.
37
Greene, Chad A., Alex S. Gardner, and Lauren C. Andrews. "Detecting seasonal ice dynamics in satellite images." Cryosphere 14, no. 12 (December 2, 2020): 4365–78. http://dx.doi.org/10.5194/tc-14-4365-2020.
Повний текст джерелаАнотація:
Abstract. Fully understanding how glaciers respond to environmental change will require new methods to help us identify the onset of ice acceleration events and observe how dynamic signals propagate within glaciers. In particular, observations of ice dynamics on seasonal timescales may offer insights into how a glacier interacts with various forcing mechanisms throughout the year. The task of generating continuous ice velocity time series that resolve seasonal variability is made difficult by a spotty satellite record that contains no optical observations during dark, polar winters. Furthermore, velocities obtained by feature tracking are marked by high noise when image pairs are separated by short time intervals and contain no direct insights into variability that occurs between images separated by long time intervals. In this paper, we describe a method of analyzing optical- or radar-derived feature-tracked velocities to characterize the magnitude and timing of seasonal ice dynamic variability. Our method is agnostic to data gaps and is able to recover decadal average winter velocities regardless of the availability of direct observations during winter. Using characteristic image acquisition times and error distributions from Antarctic image pairs in the ITS_LIVE dataset, we generate synthetic ice velocity time series, then apply our method to recover imposed magnitudes of seasonal variability within ±1.4 m yr−1. We then validate the techniques by comparing our results to GPS data collected on Russell Glacier in Greenland. The methods presented here may be applied to better understand how ice dynamic signals propagate on seasonal timescales and what mechanisms control the flow of the world’s ice.
38
Burgess, E. W., R. R. Forster, C. F. Larsen, and M. Braun. "Surge dynamics on Bering Glacier, Alaska, in 2008–2011." Cryosphere 6, no. 6 (November 7, 2012): 1251–62. http://dx.doi.org/10.5194/tc-6-1251-2012.
Повний текст джерелаАнотація:
Abstract. A surge cycle of the Bering Glacier system, Alaska, is examined using observations of surface velocity obtained using synthetic aperture radar (SAR) offset tracking, and elevation data obtained from the University of Alaska Fairbanks LiDAR altimetry program. After 13 yr of quiescence, the Bering Glacier system began to surge in May 2008 and had two stages of accelerated flow. During the first stage, flow accelerated progressively for at least 10 months and reached peak observed velocities of ~ 7 m d−1. The second stage likely began in 2010. By 2011 velocities exceeded 9 m d−1 or ~ 18 times quiescent velocities. Fast flow continued into July 2011. Surface morphology indicated slowing by fall 2011; however, it is not entirely clear if the surge is yet over. The quiescent phase was characterized by small-scale acceleration events that increased driving stresses up to 70%. When the surge initiated, synchronous acceleration occurred throughout much of the glacier length. Results suggest that downstream propagation of the surge is closely linked to the evolution of the driving stress during the surge, because driving stress appears to be tied to the amount of resistive stress provided by the bed. In contrast, upstream acceleration and upstream surge propagation is not dependent on driving stress evolution.
39
Sun, Zhiliang, Lingwei Kong, Wei Bai, and Yong Wang. "Seismic Performance of Deposit Slopes with Underlying Bedrock before and after Reinforcement by Stabilizing Piles." Applied Sciences 11, no. 12 (June 18, 2021): 5664. http://dx.doi.org/10.3390/app11125664.
Повний текст джерелаАнотація:
The seismic performance of stabilizing piles used to reinforce underlying bedrock in a deposit slope is a complex soil–structure interaction problem. Two centrifuge shaking table model testswere conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilizing piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. The differencesin the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The presence of the rock-socketed stabilizing piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part. With increases in the peak ground acceleration of the input motion, the resistance of the bedrock in front of the stabilizing piles increases and the peak resistance under the bedrock surface of the stabilizing piles gradually moves downwards.This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilizing pile.
40
Skvarca, Pedro, Hernán De Angelis, and Andrés F. Zakrajsek. "Climatic conditions, mass balance and dynamics of Larsen B ice shelf, Antarctic Peninsula, prior to collapse." Annals of Glaciology 39 (2004): 557–62. http://dx.doi.org/10.3189/172756404781814573.
Повний текст джерелаАнотація:
AbstractFollowing the collapse of Larsen A in 1995, about 3200 km2 of Larsen B ice shelf disintegrated in early 2002 during the warmest summer recorded on the northeastern Antarctic Peninsula. Immediately prior to disintegration the last field campaign was carried out on Larsen B. Measurements included surface net mass balance, velocity and strain rate on a longitudinal transect along Crane Glacier flowline and over a remnant section confined within Seal Nunataks that survived the collapse. In addition, an automatic weather station located nearby allowed derivation of melt days relevant to the formation and extent of surface meltwater. Repeated surveys allowed us to detect a significant acceleration in ice-flow velocity and associated increasing strain rates along the longitudinal transect. It may be possible to use this acceleration as a predictor of imminent ice-shelf collapse, applicable to ice shelves subject to similar climatic conditions. Additional information on recent ongoing changes was provided by a visible satellite image acquired in early 2003.
41
Dub, Martin, Josef Kolář, František Lopot, Vojtěch Dynybyl, and Ondřej Berka. "Stress and Motion Analysis of Tram Gearbox Hinge." Applied Mechanics and Materials 732 (February 2015): 223–26. http://dx.doi.org/10.4028/www.scientific.net/amm.732.223.
Повний текст джерелаАнотація:
During working of tram the chassis are dynamically loaded through acceleration, deceleration, passage curves and evidently by the roughness of the rail track. These added dynamic loads can significantly increase wearing of the chassis components and drive. In the case of tested tram problems with bearing housing into gear box occurred. Too rigid hinge bedding can cause additional parasitic load to bearings. It is desirable to investigate its stress state during acceleration, deceleration and other common drive regimes. For this purpose, strain gauges are used. Moreover, for the verification and better description of gearbox suspension behaviour, the Qualisys system for capturing and evaluating motion is used. Acquired data are processed in software Matlab and in user interface of the Qualisys software.
42
Habermann, M., M. Truffer, and D. Maxwell. "Changing basal conditions during the speed-up of Jakobshavn Isbræ, Greenland." Cryosphere Discussions 7, no. 3 (June 1, 2013): 2153–90. http://dx.doi.org/10.5194/tcd-7-2153-2013.
Повний текст джерелаАнотація:
Abstract. Ice-sheet outlet glaciers can undergo dynamic changes such as the rapid speed-up of Jakobshavn Isbræ following the disintegration of its floating ice tongue. These changes are associated with stress changes on the boundary of the ice mass. We investigate the basal conditions throughout a well-observed period of rapid change and evaluate parameterizations currently used in ice-sheet models. A Tikhonov inverse method with a Shallow Shelf Approximation forward model is used for diagnostic inversions for the years 1985, 2000, 2005, 2006 and 2008. Our ice softness, model norm, and regularization parameter choices are justified using the data-model misfit metric and the L-curve method. The sensitivity of the inversion results to these parameter choices is explored. We find a lowering of basal yield stress in the first 7 km of the 2008 grounding line and no significant changes higher upstream. The temporal evolution in the fast flow area is in broad agreement with a Mohr–Coulomb parameterization of basal shear stress, but with a till friction angle much lower than has been measured for till samples. The lowering of basal yield stress is significant within the uncertainties of the inversion, but it cannot be ruled out that there are other significant contributors to the acceleration of the glacier.
43
MOYER, A. N., P. W. NIENOW, N. GOURMELEN, A. J. SOLE, D. A. SLATER, M. TRUFFER, and M. FAHNESTOCK. "Spatio-temporal variations in seasonal ice tongue submarine melt rate at a tidewater glacier in southwest Greenland." Journal of Glaciology 65, no. 252 (May 27, 2019): 523–30. http://dx.doi.org/10.1017/jog.2019.27.
Повний текст джерелаАнотація:
ABSTRACTSubmarine melting of tidewater glaciers is proposed as a trigger for their recent thinning, acceleration and retreat. We estimate spring submarine melt rates (SMRs) of Kangiata Nunaata Sermia in southwest Greenland, from 2012 to 2014, by examining changes in along-fjord freeboard and velocity of the seasonal floating ice tongue. Estimated SMRs vary spatially and temporally near the grounding line, with mean rates of 1.3 ± 0.6, 0.8 ± 0.3 and 1.0 ± 0.4 m d−1across the tongue in 2012, 2013 and 2014, respectively. Higher melt rates correspond with locations of emerging subglacial plumes and terminus calving activity observed during the melt season using time-lapse camera imagery. Modelling of subglacial flow paths suggests a dynamic system capable of rapid re-routing of subglacial discharge both within and between melt seasons. Our results provide an empirically-derived link between the presence of subglacial discharge plumes and areas of high spring submarine melting and calving along glacier termini.
44
Burgess, E. W., R. R. Forster, C. F. Larsen, and M. Braun. "Surge dynamics on Bering Glacier, Alaska, in 2008–2011." Cryosphere Discussions 6, no. 2 (March 21, 2012): 1181–204. http://dx.doi.org/10.5194/tcd-6-1181-2012.
Повний текст джерелаАнотація:
Abstract. A 2008–2011 surge of Bering Glacier, Alaska is examined using observations of surface velocity and surface elevation change. Velocity measurements are obtained using synthetic aperture radar (SAR) offset tracking and elevation data are obtained from the University of Alaska Fairbanks LiDAR altimetry program. Bering Glacier began to surge in May 2008 and had two phases of accelerated flow. The first phase accelerated progressively for at least 10 months and reached peak observed velocities of ~7 m d−1. Results suggest that during the quiescent phase, prior to the surge, periods of accelerated flow increased driving stresses up to 70% in a ~10 km-long section of the Lower Bering. When the first phase of the surge initiated, synchronous acceleration occurred throughout much of the glacier length, indicating widespread pressurization of the bed, but the largest accelerations initiated at the location where driving stress built up during quiescence. From there, rapid flow velocities propagated upstream and downstream across much of the glacier length and transpired as small, transient and unorganized propagation fronts. The second phase occurred in 2011 and was of comparable scale to the surge in 1993–1995, with velocities exceeding 9 m d−1 or ~18 times quiescent velocities.
45
Taratorkin, Alexander, Viktor Derzhanskii, and Igor Taratorkin. "Oscillation damping in the powertrain unit of transport vehicles." MATEC Web of Conferences 287 (2019): 01021. http://dx.doi.org/10.1051/matecconf/201928701021.
Повний текст джерелаАнотація:
The paper presents the results of an analytical experimental research of conditions for excitation of oscillatory processes in steady-state conditions and in the process of starting-up an engine equipped with a modern Common Rail fuel supply control system. Based on the results of mathematical simulation, the dependence of the dynamic torque amplitude on boosting acceleration during engine start-up and on the parameters of the elastic-dissipative coupling (connection) of the engine with the transmission is analyzed. It establishes the rationale for a possibility of optimizing the fuel supply system control algorithms for a modern diesel engine, taking into consideration the dependence of the process on the properties of the transmission and the peculiarities of its operation.
46
MERKISZ, Jerzy, and Marek WALIGÓRSKI. "Numerical method of vibroacoustic estimators analysis in a frequency domain for IC engine." Combustion Engines 154, no. 3 (September 1, 2013): 25–33. http://dx.doi.org/10.19206/ce-116982.
Повний текст джерелаАнотація:
The paper describes the assessment of the main processes taking place in a IC engine. The article concerns vibroacoustic processes. Authors chosen vibration ones to the research. In view of the characteristics that the above processes have for the diagnosis of the slow andfast processes taking place during combustion, it was necessary to take into account them for periodic and on-line analyses of technical state and correctness of the engine dynamic processes run. Evaluations of the possibility of the method application were performed in the point of view of the diagnostic analysis and its use in the diagnostic system for combustion process and in the aspect of the limitation of excessive emission sources (occurred by incorrect processes runs or by functional characteristics decrease of the object or by potential failures of the elements and subassemblies during exploitation). Method analysis of vibration acceleration generated in an engine, basing on diagnostics theory use, with the help of which quantitive components obtained from the frequency-domain processes runs were searched. Diagnostic estimators were the measures of the quantity assessment, changes of which were the subject ofpresented analyses. Limits and qualification guidelines of an incorrect process are also in a paper. Diagnostic algorithms of misfire detection for the present and future vehicles combustion engines (also for hybrid vehicles) and in the aspect of OBDIII or OBMsystems application are taken into account.
47
Pelenyte-Vyšniauskiene, Lina, and Algirdas Jurkauskas. "RESEARCH INTO OCCUPANT'S MOTION IN VEHICLES DURING CRASHES." TRANSPORT 19, no. 4 (August 31, 2004): 184–90. http://dx.doi.org/10.3846/16484142.2004.9637974.
Повний текст джерелаАнотація:
Traffic accidents depend on many factors and circumstances. Important data are registered by taking photos of the accident place, measuring the deformations of vehicles and skidding and sliding traces. Weather conditions, drivers’ and pedestrian's actions are also taken into account. However the existing data are far from sufficient to conduct a research into traffic accidents. In such cases mathematical modelling and the application of computer programs are very helpful. This article deals with the processes during the collision of vehicles as well as the occupant's dynamics inside the vehicle. The research studies on what the occupant motion depends and what is the power balance between the occupant and safety means. The article offers a way of evaluating injuries, measuring the occupants’ acceleration and velocity, taking into account different distances inside the vehicle during an accident.
48
Flegner, Patrik, Ján Kačur, Milan Durdán, and Marek Laciak. "Evaluation of the Acceleration Vibration Signal for Aggregates of the Horizontal Drilling Stand." Applied Sciences 12, no. 8 (April 14, 2022): 3984. http://dx.doi.org/10.3390/app12083984.
Повний текст джерелаАнотація:
During the operation of each machine, there are dynamic effects causing vibrations. Such a device is also an experimental horizontal drilling stand with aggregates, i.e., a direct current motor (DC), a pump, and a hydro-generator. During their operation, unwanted vibration acceleration signals are generated. It is clear that the accompanying vibration signal carries integrating information about the current state of the drilling rig. Vibration signal processing methods for the time and frequency domains were used. The results of time-domain processing showed significant differences in time waveforms, statistical characteristics, and auto-correlation functions. The auto-correlation function pointed to the periodicity and dependence of the vibrational signal samples. Based on the acquired knowledge, the signals were classified, and a strong source of vibration was determined. Noise is superimposed on the harmonic components of the signals. Amplitude and power spectra were constructed in the frequency domain. Dominant frequencies were identified for each investigated mode in the operating mode. Power spectra removed less significant frequencies and focused on the dominant ones. Time-frequency spectrograms revealed significantly higher frequency bands. The proposed methods can be implemented in diagnosing the operation of the machine and aggregates, determining the source of the greatest vibrations, wear of parts of the equipment such as the drill bit, and recognition of the overall condition of the equipment.
49
Habermann, M., M. Truffer, and D. Maxwell. "Changing basal conditions during the speed-up of Jakobshavn Isbræ, Greenland." Cryosphere 7, no. 6 (November 7, 2013): 1679–92. http://dx.doi.org/10.5194/tc-7-1679-2013.
Повний текст джерелаАнотація:
Abstract. Ice-sheet outlet glaciers can undergo dynamic changes such as the rapid speed-up of Jakobshavn Isbræ following the disintegration of its floating ice tongue. These changes are associated with stress changes on the boundary of the ice mass. We invert for basal conditions from surface velocity data throughout a well-observed period of rapid change and evaluate parameterizations currently used in ice-sheet models. A Tikhonov inverse method with a shallow-shelf approximation forward model is used for diagnostic inversions for the years 1985, 2000, 2005, 2006 and 2008. Our ice-softness, model norm, and regularization parameter choices are justified using the data-model misfit metric and the L curve method. The sensitivity of the inversion results to these parameter choices is explored. We find a lowering of effective basal yield stress in the first 7 km upstream from the 2008 grounding line and no significant changes higher upstream. The temporal evolution in the fast flow area is in broad agreement with a Mohr–Coulomb parameterization of basal shear stress, but with a till friction angle much lower than has been measured for till samples. The lowering of effective basal yield stress is significant within the uncertainties of the inversion, but it cannot be ruled out that there are other significant contributors to the acceleration of the glacier.
50
Zhang, Xudong, Jinjun Xiong, and Angela M. Bishop. "Effects of Load and Speed on Lumbar Vertebral Kinematics during Lifting Motions." Human Factors: The Journal of the Human Factors and Ergonomics Society 45, no. 2 (June 2003): 296–306. http://dx.doi.org/10.1518/hfes.45.2.296.27242.
Повний текст джерелаАнотація:
This experimental study investigated the effects of load magnitude and movement speed on lumbar vertebral kinematics during lifting task performance. Ten participants performed sagittally symmetric lifting movements with systematically varied load using either a normal or a faster-than-normal speed. Skin-surface markers were strategically placed over the participants' spinous processes and other landmarks representing major body joints and were recorded during the movements by a motion capture system. The center of rotation (COR) locations and segmental movement profiles for lumbar vertebrae L2 to L5 were derived and analyzed. Results suggested that (a) the COR locations and vertebral angular displacement were not significantly affected by the speed or load variation; (b) a faster speed tended to shorten the time to complete the acceleration for all the lumbar vertebrae considered; and (c) the load increase incurred a tendency for the L5 to complete the primary displacement in a briefer time while enduring greater peak acceleration and velocity. The findings lead to a better understanding of the relation between lifting dynamics and spinal motion. Potential applications of this research include the development of more accurate biomechanical models and software tools for depicting spinal motions and quantifying low-back stress.